5.查询数据

第一节：单表查询















第一节：单表查询

SELECT id,stuName,age,sex,gradeName FROM t_student ;

SELECT stuName,id,age,sex,gradeName FROM t_student ;

SELECT * FROM t_student;

SELECT stuName,gradeName FROM t_student;

SELECT * FROM t_student WHERE id=1;

SELECT * FROM t_student WHERE age>22;

SELECT * FROM t_student WHERE age IN (21,23);
SELECT * FROM t_student WHERE age NOT IN (21,23);

SELECT * FROM t_student WHERE age BETWEEN 21 AND 24;
SELECT * FROM t_student WHERE age NOT BETWEEN 21 AND 24;

SELECT * FROM t_student WHERE stuName LIKE '张三';
SELECT * FROM t_student WHERE stuName LIKE '张三%';
SELECT * FROM t_student WHERE stuName LIKE '张三__';
SELECT * FROM t_student WHERE stuName LIKE '%张三%';

SELECT * FROM t_student WHERE sex IS NULL;
SELECT * FROM t_student WHERE sex IS NOT NULL;

SELECT * FROM t_student WHERE gradeName='一年级' AND age=23
SELECT * FROM t_student WHERE gradeName='一年级' OR age=23

SELECT DISTINCT gradeName FROM t_student;

SELECT * FROM t_student ORDER BY age ASC;
SELECT * FROM t_student ORDER BY age DESC;

SELECT * FROM t_student GROUP BY gradeName;

SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName HAVING COUNT(stuName)>3;

SELECT gradeName,COUNT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;
SELECT gradeName,GROUP_CONCAT(stuName) FROM t_student GROUP BY gradeName WITH ROLLUP;

SELECT * FROM t_student LIMIT 0,5;
SELECT * FROM t_student LIMIT 5,5;
SELECT * FROM t_student LIMIT 10,5;

第二节：使用聚合函数查询

SELECT COUNT(*) FROM t_grade;
SELECT COUNT(*) AS total FROM t_grade;

SELECT stuName,COUNT(*) FROM t_grade GROUP BY stuName;

SELECT stuName,SUM(score) FROM t_grade WHERE stuName="张三";

SELECT stuName,SUM(score) FROM t_grade GROUP BY stuName;

SELECT stuName,AVG(score) FROM t_grade WHERE stuName="张三";

SELECT stuName,AVG(score) FROM t_grade GROUP BY stuName;

SELECT stuName,course,MAX(score) FROM t_grade WHERE stuName="张三";

SELECT stuName,MAX(score) FROM t_grade GROUP BY stuName;

SELECT stuName,course,MIN(score) FROM t_grade WHERE stuName="张三";

SELECT stuName,MIN(score) FROM t_grade GROUP BY stuName;

第三节：连接查询

SELECT * FROM t_book,t_bookType;

SELECT * FROM t_book,t_bookType WHERE t_book.bookTypeId=t_bookType.id;

SELECT bookName,author,bookTypeName FROM t_book,t_bookType WHERE t_book.bookTypeId=t_bookType.id;

SELECT tb.bookName,tb.author,tby.bookTypeName FROM t_book tb,t_bookType tby WHERE tb.bookTypeId=tby.id;

SELECT * FROM t_book LEFT JOIN t_bookType ON t_book.bookTypeId=t_bookType.id;

SELECT tb.bookName,tb.author,tby.bookTypeName FROM t_book tb LEFT JOIN t_bookType tby ON tb.bookTypeId=tby.id;

SELECT * FROM t_book RIGHT JOIN t_bookType ON t_book.bookTypeId=t_bookType.id;

SELECT tb.bookName,tb.author,tby.bookTypeName FROM t_book tb RIGHT JOIN t_bookType tby ON tb.bookTypeId=tby.id;

SELECT tb.bookName,tb.author,tby.bookTypeName FROM t_book tb,t_bookType tby WHERE tb.bookTypeId=tby.id AND tb.price>70;

第四节：子查询

SELECT * FROM t_book WHERE booktypeId IN (SELECT id FROM t_booktype);

SELECT * FROM t_book WHERE booktypeId NOT IN (SELECT id FROM t_booktype);

SELECT * FROM t_book WHERE price>=(SELECT price FROM t_pricelevel WHERE priceLevel=1);

SELECT * FROM t_book WHERE EXISTS (SELECT * FROM t_booktype);

SELECT * FROM t_book WHERE NOT EXISTS (SELECT * FROM t_booktype);

SELECT * FROM t_book WHERE price>= ANY (SELECT price FROM t_pricelevel);

SELECT * FROM t_book WHERE price>= ALL (SELECT price FROM t_pricelevel);

第5，6节

SELECT id FROM t_book;

SELECT id FROM t_booktype;

SELECT id FROM t_book UNION SELECT id FROM t_booktype;

SELECT id FROM t_book UNION ALL SELECT id FROM t_booktype;

SELECT * FROM t_book WHERE id=1;

SELECT * FROM t_book t WHERE t.id=1;

SELECT t.bookName FROM t_book t WHERE t.id=1;

SELECT t.bookName bName FROM t_book t WHERE t.id=1;

SELECT t.bookName AS bName FROM t_book t WHERE t.id=1;